1 /* 2 * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 27 /* 28 * The Original Code is HAT. The Initial Developer of the 29 * Original Code is Bill Foote, with contributions from others 30 * at JavaSoft/Sun. 31 */ 32 33 package jdk.test.lib.hprof.util; 34 import java.util.*; 35 36 /** 37 * A singleton utility class that sorts a vector. 38 * <p> 39 * Use: 40 * <pre> 41 * 42 * Vector v = <a vector of, say, String objects>; 43 * VectorSorter.sort(v, new Comparer() { 44 * public int compare(Object lhs, Object rhs) { 45 * return ((String) lhs).compareTo((String) rhs); 46 * } 47 * }); 48 * </pre> 49 * 50 * @author Bill Foote 51 */ 52 53 54 public class VectorSorter { 55 56 /** 57 * Sort the given vector, using c for comparison 58 **/ 59 static public void sort(Vector<Object> v, Comparer c) { 60 quickSort(v, c, 0, v.size()-1); 61 } 62 63 64 /** 65 * Sort a vector of strings, using String.compareTo() 66 **/ 67 static public void sortVectorOfStrings(Vector<Object> v) { 68 sort(v, new Comparer() { 69 public int compare(Object lhs, Object rhs) { 70 return ((String) lhs).compareTo((String) rhs); 71 } 72 }); 73 } 74 75 76 static private void swap(Vector<Object> v, int a, int b) { 77 Object tmp = v.elementAt(a); 78 v.setElementAt(v.elementAt(b), a); 79 v.setElementAt(tmp, b); 80 } 81 82 // 83 // Sorts v between from and to, inclusive. This is a quick, off-the-top- 84 // of-my-head quicksort: I haven't put any thought into optimizing it. 85 // I _did_ put thought into making sure it's safe (it will always 86 // terminate). Worst-case it's O(n^2), but it will usually run in 87 // in O(n log n). It's well-behaved if the list is already sorted, 88 // or nearly so. 89 // 90 static private void quickSort(Vector<Object> v, Comparer c, int from, int to) { 91 if (to <= from) 92 return; 93 int mid = (from + to) / 2; 94 if (mid != from) 95 swap(v, mid, from); 96 Object pivot = v.elementAt(from); 97 // Simple-minded, but reasonable 98 int highestBelowPivot = from - 1; 99 int low = from+1; 100 int high = to; 101 // We now move low and high toward eachother, maintaining the 102 // invariants: 103 // v[i] <= pivot for all i < low 104 // v[i] > pivot for all i > high 105 // As long as these invariants hold, and every iteration makes 106 // progress, we are safe. 107 while (low <= high) { 108 int cmp = c.compare(v.elementAt(low), pivot); 109 if (cmp <= 0) { // v[low] <= pivot 110 if (cmp < 0) { 111 highestBelowPivot = low; 112 } 113 low++; 114 } else { 115 int c2; 116 for (;;) { 117 c2 = c.compare(v.elementAt(high), pivot); 118 // v[high] > pivot: 119 if (c2 > 0) { 120 high--; 121 if (low > high) { 122 break; 123 } 124 } else { 125 break; 126 } 127 } 128 // At this point, low is never == high 129 if (low <= high) { 130 swap(v, low, high); 131 if (c2 < 0) { 132 highestBelowPivot = low; 133 } 134 low++; 135 high--; 136 } 137 } 138 } 139 // Now we just need to sort from from..highestBelowPivot 140 // and from high+1..to 141 if (highestBelowPivot > from) { 142 // pivot == pivot, so ensure algorithm terminates 143 swap(v, from, highestBelowPivot); 144 quickSort(v, c, from, highestBelowPivot-1); 145 } 146 quickSort(v, c, high+1, to); 147 } 148 }